On Mon, Mar 31, 2008 at 12:50 PM, Leo <neleo@xxxxxxx> wrote:
Here comes the tcpdump (the server has IP 192.168.1.1 listening on port
3306 and the client has IP 192.168.1.99).
tcpdump on the server:
11:24:44.226373 IP 192.168.1.99.39028 > 192.168.1.1.3306: S
3068401272:3068401272(0) win 5840 <mss 1460,sackOK,timestamp 10592352
0,nop,wscal e 6>
11:24:44.226389 IP 192.168.1.1.3306 > 192.168.1.99.39028: S
3052139931:3052139931(0) ack 3068401273 win 5792 <mss
1460,sackOK,timestamp 10478 87 10592352,nop,wscale 7>
11:24:47.226673 IP 192.168.1.99.39028 > 192.168.1.1.3306: S
3068401272:3068401272(0) win 5840 <mss 1460,sackOK,timestamp 10595352
0,nop,wscale 6>
11:24:47.226715 IP 192.168.1.1.3306 > 192.168.1.99.39028: S
3052139931:3052139931(0) ack 3068401273 win 5792 <mss
1460,sackOK,timestamp 1048187 10592352,nop,wscale 7>
11:24:47.226957 IP 192.168.1.99.39028 > 192.168.1.1.3306: . ack 1 win 92
<nop,nop,timestamp 10595352 1048187>
11:24:47.227488 IP 192.168.1.99.39028 > 192.168.1.1.3306: F 1:1(0) ack 1
win 92 <nop,nop,timestamp 10595352 1048187>
11:24:47.227580 IP 192.168.1.1.3306 > 192.168.1.99.39028: F 1:1(0) ack 2
win 46 <nop,nop,timestamp 1048187 10595352>
11:24:47.227810 IP 192.168.1.99.39028 > 192.168.1.1.3306: . ack 2 win 92
<nop,nop,timestamp 10595353 1048187>
tcpdump on the client:
11:24:44.045735 IP 192.168.1.99.39028 > 192.168.1.1.3306: S
3068401272:3068401272(0) win 5840 <mss 1460,sackOK,timestamp 10592352
0,nop,wscale 6>
11:24:47.045710 IP 192.168.1.99.39028 > 192.168.1.1.3306: S
3068401272:3068401272(0) win 5840 <mss 1460,sackOK,timestamp 10595352
0,nop,wscale 6>
11:24:47.045911 IP 192.168.1.1.3306 > 192.168.1.99.39028: S
3052139931:3052139931(0) ack 3068401273 win 5792 <mss
1460,sackOK,timestamp 1048187 10592352,nop,wscale 7>
11:24:47.046015 IP 192.168.1.99.39028 > 192.168.1.1.3306: . ack 1 win 92
<nop,nop,timestamp 10595352 1048187>
11:24:47.046541 IP 192.168.1.99.39028 > 192.168.1.1.3306: F 1:1(0) ack 1
win 92 <nop,nop,timestamp 10595352 1048187>
11:24:47.046845 IP 192.168.1.1.3306 > 192.168.1.99.39028: F 1:1(0) ack 2
win 46 <nop,nop,timestamp 1048187 10595352>
11:24:47.046880 IP 192.168.1.99.39028 > 192.168.1.1.3306: . ack 2 win 92
<nop,nop,timestamp 10595353 1048187>
I can also provide a strace if required (alternatively you can find the
tcpdump and the strace in my original posting, e.g.
http://marc.info/?l=linux-net&m=120214156112338&w=2).
Kind regards,
Leo
Well, the server sends back the SYN/ACK. Your client is not receiving it...
Normally I will say a network problem (switch / router), please check
that once more.
(There is / was a bug in PCAP before which lost packages in tcpdump,
but this seams not be the case here)
Br H.Willstrand
H. Willstrand wrote:
> On Mon, Mar 31, 2008 at 11:33 AM, Leo <neleo@xxxxxxx> wrote:
>
>> Yes, we have changed the back_log settings in my.cnf. We also tried
>> various combinations of the kernel parameters you mentioned in your
>> email - without success.
>>
>> Have you made any changes on the client (=webserver)? Perhaps it's not a
>> problem of the server (=mysql). As I figured out in my original posting
>> it looks as if the client didn't receive the SYN/ACK package from the
>> server (keep in mind that it is reproducable with lo interface,
>> therefore it's not a hardware problem with cables, switches, ...):
>>
>> "When you look at the TCP pakets transmitted between server and client
>> (tcpdump) you will see that the client sends a SYN and the server
>> answers with a SYN/ACK. However the client will never receive the
>> SYN/ACK. Therefore the client resends a SYN after exactly 3 seconds. The
>> server answers with a SYN/ACK again and this time the client receives
>> the paket. Now the connection is working."
>>
>>
>
> Hi!
>
> Can you please post that tcpdump? (Just to check the first ACK).
>
> Br H.Willstrand
>
>
>> On friday I received an email from another user having the same problem.
>> As I mentioned in my last email: we are not alone ;-)
>>
>> Many thanks for your help.
>>
>> Kind regards,
>> Leo
>>
>>
>>
>> Marlon de Boer wrote:
>> > Leo wrote:
>> >
>> >> We discovered the same problem two month ago (even 3 sec connect
>> >> problems between webserver and mysql backend). I have posted it to
>> >> the list (subject "TCP connect hangs for 3 seconds", 2008-02-04)
>> >> but didn't get any answer yet. When I read your mail it was a
>> >> flicker of hope.
>> >>
>> >> This is not a mysql issue! You can easily reproduce it with a few
>> >> lines of C code (see below, it's similar to your program) running
>> >> against any open port on the server (e.g. netcat: nc -k -l
>> >> <PORTNUMBER>). We have also tested it on different hardware and
>> >> kernel versions (up to 2.6.24.4) and we can deliver further
>> >> information if requested ...
>> >>
>> >> Unfortunately the kernel parameter you mentioned in your second
>> >> mail (net.core.somaxconn) didn't solve the problem.
>> >>
>> >> I think there are many other people out there having this problem
>> >> unconsciously. Can anybody help?
>> >>
>> >>
>> > I used the c code below to test the server side. After playing with
>> > the kernel settings, some code,
>> > setsockopt(sd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt)) and
>> > listen(sd, 8192) the timeouts disappeared.
>> >
>> > Did you changed the settings in mysql.cnf? back_log = 8192, and
>> > restarted the mysql daemon? Else try to raise it to 16384 or even higher.
>> >
>> > Regards
>> > Marlon
>> >
>> >
>>
>>
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